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Since the dawn of humanity,

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an estimated 100.8 billion
people have lived and died,

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a number that increases by about
.8% of the world's population each year.

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What happens to all 
of those people's bodies after they die

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and will the planet eventually
run out of burial space?

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When a person's heart stops beating,

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the body passes through several
stages before it begins decomposing.

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Within minutes after death,

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the blood begins settling in
the lower-most parts of the body.

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Usually eight to twelve hours later,

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the skin in those areas is discolored
by livor mortis, or post-mortem stain.

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And while at the moment of death
the body's muscles relax completely

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in a condition called primary flaccidity,

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they stiffen about two to six hours later
in what's known as rigor mortis.

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This stiffening spreads 
through the muscles,

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and its speed can be affected by age,
gender, and the surrounding environment.

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The body also changes temperature,

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usually cooling off 
to match its environment.

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Next comes decomposition,

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the process by which bacteria and insects
break apart the body.

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Many factors affect 
the rate of decomposition.

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There is, however, a basic guide of the
effect of the environment on decompositon

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called Casper's Law.

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It says that if all other 
factors are equal,

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a body exposed to air decomposes twice
as fast as one immersed in water

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and eight times as fast 
as one buried in earth.

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Soil acidity also greatly 
affects bone preservation.

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High-acidity soils with 
a pH of less than 5.3

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will rapidly decompose bone,

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whereas in a neutral or basic soil
with a pH of 7 or more,

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a skeleton can remain in relatively
good condition for centuries.

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Different cultures throughout history have
developed unique approaches to burials.

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As far back as 
the first Neanderthal burials,

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death was accompanied by rituals,

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like the positioning, coloring,
or decorating of corpses.

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Traditional Christian burials decorate
the body in dress,

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while in traditional Islam,

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a body is wrapped in a piece 
of ritual fabric

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with the face oriented toward Mecca.

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Traditional Hindus ceremonially burn
the body,

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and Zoroastrians, followers of one of the
oldest monotheistic religions,

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traditionally place bodies atop a tower
to expose them to the Sun

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and scavenging birds.`

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Before the Industrial Revolution,
burials were simple and accessible.

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These days, with suitable burial land
running out in high-population areas,

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purchasing private gravesites
can be costly,

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and many people can't afford
simple burials.

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Even cremation, the second most common
burial practice in the world,

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comes with a high cost.

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As for the question 
of running out of space,

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the issue isn't so much about total land
in the world

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as it is that large populations cluster
together within cities.

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Most of the big cities in the world

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may run out of suitable burial grounds
within a century.

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For London, it's even sooner.

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That may happen by 2035.

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So are there alternatives
to traditional burials

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that might help with the space issue?

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In some countries, skyscraper cemeteries
enable vertical burials.

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Some options focus on the body's
relationship with the environment.

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Promession, for example, freeze-dries
and pulverizes the body,

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creating a powder 
that can turn into compost

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when mixed with oxygen and water.

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There are also green burials that use
special materials,

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such as biodegradable caskets,

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urns that sprout trees,

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and burial suits that grow mushrooms.

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Eternal reefs take that concept
to the depths of the ocean

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using a mixture of ashes and cement
to create marine habitats for sea life.

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Death is an inevitable part
of the human condition,

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but how we treat bodies and burials
continues to evolve.

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We may each have different spiritual,

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religious,

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or practical approaches to dying,

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but the ever-increasing demand
for burial space

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might give us a push to be creative

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about where our bodies go
after the final stages of life.